In Altair, is there a way to draw attention of the viewer to a particular point on a time-series chart?
For example, by drawing a circle around the data point:
and then allowing a custom text to be displayed in a tooltip?
Thank you!
1 Answers
You can do this with a layer chart; for example:
import altair as alt
import pandas as pd
import numpy as np
rng = np.random.default_rng(0)
data = pd.DataFrame({
'x': pd.date_range('2021-01-01', freq='W', periods=52),
'y': rng.normal(size=52).cumsum()
})
line = alt.Chart(data).mark_line().encode(
x='x',
y='y',
)
callout = alt.Chart(data.iloc[7:8]).mark_point(
color='red', size=300, tooltip="Tooltip text here"
).encode(
x='x',
y='y'
)
line + callout
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